Small Scale Microencapsulated Pigments And Uses Thereof

ABSTRACT

A method is provided for making thermochromic pigments in microcapsules having unusually small particle sizes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Division of U.S. patent application Ser. No.13/843,492 filed Mar. 15, 2013, which is incorporated herein byreference in its entirety.

FIELD

This disclosure pertains to the field of thermochromic pigment systems.More particularly, these are reversible thermochromic systems having acontrollable color transition range across a hysteresis window of thesystem, as well as photochromic systems and combinations of photochromicand thermochromic systems.

BACKGROUND

Dyes that change color over a range of temperatures are known asthermochromic dyes. Thermochromic dyes can be manufactured to have acolor change that is reversible or irreversible. Formulated as pigmentsor colorants, they are used in a variety of applications such as plasticmasterbatch, paper, textiles, coatings, offset ink, metal decoratinginks, coatings, ultraviolet radiation curable inks and coatings, solventbased inks and coatings, screen inks and coatings, gravure inks andcoatings, paints, security printing, brand protection, smart packaging,marketing and novelty printing, among other uses.

Thermochromic dyes use colorants that are either liquid crystals orleuco dyes. Liquid crystals are used less frequently than leuco dyesbecause they are very difficult to work with and require highlyspecialized printing and handling techniques.

Thermochromic dyes are a system of interacting parts. The parts of thesystem are leuco dyes acting as colorants, weak organic acids acting ascolor developers and solvents that variably interact with components ofthe system according to the temperature of the system. Thermochromic dyesystems are microencapsulated in a protective coating to protect thecontents from undesired effects from the environment. Each microcapsuleis self-contained, having all of the components of the entire systemrequired to reproduce the color change. The components of the systeminteract with one another differently at different temperatures.Generally, the system is ordered and colored below a temperaturecorresponding to the full color point. The system begins to lose itscolor at a temperature corresponding to a predetermined activationtemperature.

Below the activation temperature, the system is colored and above theactivation temperature they are clear or lightly colored. The activationtemperature corresponds to a range of temperatures at which thetransition is taking place between the full color point and the clearingpoint. Generally, the activation temperature is defined as thetemperature at which the human eye can perceive that the system isstarting to lose color, or alternatively, starting to gain color.Presently, thermochromic systems are designed to have activationtemperatures over a broad range, from about −20° C. to about 80° C. orhigher. With heating, the system becomes increasingly unordered andcontinues to lose its color until it reaches a level of disorder at atemperature corresponding to a clearing point. At the clearing point,the system lacks any recognizable color.

Specific thermochromic ink formulations are known in the art. See, forexample, U.S. Pat. Nos. 4,720,301, 5,219,625 5,558,700, 5,591,255,5,997,849, 6,139,779, 6,494,950 and 7,494,537, all of which areexpressly incorporated herein by reference to the same extent as thoughfully replicated herein. These thermochromic inks are known to usevarious components in their formulations, and are generally reversiblein their color change. Thermochromic inks are available in variouscolors, with various activation temperatures, clearing points and fullcolor points. Thermochromic inks may be printed by offset litho, dryoffset, letterpress, gravure, flexo and screen processes, amongstothers. Thermochromic inks containing leuco dyes are available for allmajor ink types such as water-based, ultraviolet cured and epoxy. Theproperties of these inks differ from process inks. For example, mostthermochromic inks contain the thermochromic systems as microcapsules,which are not inert and insoluble as are ordinary process pigments. Thesize of the microcapsules containing the thermochromic systems rangestypically between 3-5 μm which is more than 10-times larger than typicalpigment particles as found in most inks. The post-print functionality ofthermochromic inks can be adversely affected by ultraviolet light,temperatures in excess of 140° C. and aggressive solvents. The lifetimeof these inks is sometimes very limited because of the degradationcaused by exposure to ultraviolet light from sunlight. Thus, there is aneed in the art for thermochromic systems in inks and coatings havingresistance to degradation from exposure to ultraviolet light.

Temperature changes in thermochromic systems are associated with colorchanges. If this change is plotted on a graph having axes of temperatureand color, the curves do not align and are offset between the heatingcycle and the cooling cycle. The entire color versus temperature curvehas the form of a loop. See generally FIG. 1A where the extent of colorchange presents a gap 100 a that differs between color change thatoccurs upon heating 102 versus cooling 103. FIG. 1B presents arelatively larger gap 100 b. Such a result shows that the color of athermochromic system does not depend only on temperature, but also onthe thermal history, i.e. whether the particular color was reachedduring heating or during cooling. This phenomenon is generally referredto as a hysteresis cycle and specifically referred to herein as colorhysteresis or the hysteresis window. Decreasing the width of thishysteresis window to approximately zero would allow for a single valuefor the full color point and a single value for the clearing point. Thiswould allow for a reliable color transition to be observed regardless ofwhether the system is being heated or cooled. Nonetheless, the conceptof decreasing separation across the hysteresis window is elusive inpractice. The extent of the respective gaps 100 a, 100 b to producecontrolled hysteresis may be practiced according to theinstrumentalities described herein.

Prior art reveals that the color transition range of microencapsulatedthermochromic systems may be adjusted by shifting the full color pointupward toward the clearing point, or shifting the clearing pointdownward toward the full color point, as explained in U.S. Pat. No.4,028,118 issued to Norikazu et al. See also EP0480162 to Masayasu etal. These shifts are accomplished by adding high melting point materialsto increase the full color point or, alternatively, by adding lowmelting point materials to the system to decrease the clearing point.Thus, the full color point or clearing point may be lowered or raised,but the overall temperature range between the two points remainsunchanged because the amount of separation or width across thehysteresis window is left largely unaffected.

In recent years, metal decoration inks have been adapted for use orthermochromic pigments in high speed commercial canning operations. Inone example of this, a thermochromic pigment may be formulated to usemelamine formaldehyde microcapsules having an average diameter from 3 to5 microns. This is poorly suited for use as a metal decoration ink forhigh speed application to a metal can where the line speed of the cancoater may be greater than 1000 or 2000 cans per minute. The use ofthermochromic metal decorating ink increasingly becomes a limitingfactor at higher production line speeds. Problems arise in the inkrheology with this particle size that leads to misting as the ink istransferred at very high speed.

Presently, the use of thermochromic pigments in inkjet inks is notpossible because creating particles sizes below one micron has not beenpossible. The larger particles interfere with the inks in the intendedenvironment of use.

SUMMARY

The presently disclosed instrumentalities overcome the problems outlinedabove and advance the art by providing a process for producing largebatches of encapsulated slurries with much smaller particle size. Thesesmaller capsules, for example, may be described in various ways. Thepigments have Gaussian distributed particle diameters primarily rangingfrom about 400 nm to 1.5 microns plus or minus 10%. By way of example,70% of the total volume of microcapsules may be of sub-micron dimensionsand about 90% are less than 1.5 microns. The pigments may also beendescribed as having mean particle diameter, as assessed by volume ofparticle, of less than 1 micron. These calculations assume sphericalparticles.

These pigments may be used to make inks that show considerably lessmisting and better transfer to metal cans at high production linespeeds, such as speeds exceeding 1000, 1500, or 2000 cans per minute.

The small particle size also facilitates the commercial use ofthermochromic pigments in systems where larger particle size isproblematic. By way of example, printed images may now be provided withfiner lines, sharper definition and improved color density than waspreviously possible when using thermochromic inks. Thermochromicpigments may now be used in ink jet printing applications.

In one aspect, the present disclosure addresses microencapsulatedpigment formulations and processing for preparing compositions that maybe used in inkjet printing applications.

In one aspect, the present disclosure addresses microencapsulatedpigment formulations and processing for preparing compositions that maybe used to improve performance in offset printing processes.

In an embodiment, these microcapsules are made of a cured amineformaldehyde resin, and the wall encapsulates an internal phaseincluding a thermochromic system or a photochromic material. Thesepigments may be dispersed in an ink vehicle that is used for printing,such as a conventional ink vehicle or carrier as may be used in offsetlitho, dry offset, letterpress, gravure, flexo and screen processes. Theink may also be an inkjet ink. These pigments may also be dispersed invehicles or carriers for coatings. Metal decoration coatings where thepigment is dispersed in a curable synthetic resin are particularlypreferred. By way of example, the microencapsulation techniques arecompatible with thermochrornic systems that achieve a blue color when ina color-activated state. This color may alternatively be any other colorknown to be achieved by thermochromic systems, such as green, yellow,black or cyan, as well as mixtures of these colors.

In one aspect, these advantages are achieved by improving conventionalmicroencapsulation processes by using a sufficient amount of surfactantdispersed in water to emulsify an internal phase to dimensions such thatupon completing a subsequent step of microencapsulating the internalphase with a cured resin the resulting slurry contains microcapsulesthat have a mean by volume particle size diameter of less than 1 micron.The surfactant may be cationic, nonionic or anionic. The surfactant, isfor example, an anionic surfactant such as maleic anhydride and/or asubstituted derivative thereof.

In one aspect, the slurry for microencapsulation is prepared bysuccessively combining under agitation: (1) an aqueous phase solutionconstituting from 40% to 70% of the slurry by weight, where from 1% to10% of the aqueous phase solution is an anionic surfactant; (2) aninternal phase mixture constituting from 23% to 35% of the slurry byweight, where from 1% to 10% by weight of the internal phase is a leucodye and from 5% to 30% is a developer for the leuco dye; (3) an amineformaldehyde resin solution constituting from 15% to 28% of the slurryby weight of which from 40% to 60% is the amine formaldehyde resinitself; and optionally (4) an accelerator for curing the amineformaldehyde resin.

DEFINITIONS

Thermochromic system—A mixture of dyes, developers, solvents, andadditives (encapsulated or non-encapsulated) that can undergo reversibleor semi-irreversible color change in response to temperature changes.

Full color point—The temperature at which a thermochromic system hasachieved maximum color density upon cooling and appears to gain nofurther color density if cooled to a lower temperature.

Activation temperature—The temperature above which the ink has almostachieved its final clear or light color end point. The color starts tofade at approximately 4° C. below the activation temperature and will bein between colors within the activation temperature range.

Clearing point—The temperature at which the color of a thermochromicsystem is diminished to a minimal amount and appears to lose no furthercolor density upon further heating.

Hysteresis—The difference in the temperature profile of a thermochromicsystem when heated from the system when cooled.

Hysteresis window—The temperature difference in terms of degrees that athermochromic system is shifted as measured between the derivative plotof chroma of a spectrophotometer reading between the cooling curve andthe heating curve.

Leuco dye—A leuco dye is a dye whose molecules can acquire two forms,one of which is colorless.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show generally the effect of controlling colorhysteresis in a thermochromic system where FIG. 1A has a narrowerhysteresis gap than does FIG. 1B;

FIG. 2 is a plot of color change versus temperature for a reversiblethermochromic dye;

FIG. 3 is a plot of color change versus temperature for a reversiblethermochromic dye; and

FIG. 4 is a process diagram that shows a process of making thermochromicpigments having very small particle diameters.

DETAILED DESCRIPTION

Conventional thermochromic systems are prepared by combining a colorforming molecule or molecules such as leuco dyes that are capable ofextended conjugation by proton gain or electron donation; a colordeveloper or developers that donate a proton or accept an electron; anda single solvent or a blend of co-solvents. The solvent or blend ofco-solvents are chosen based on melting point and establish thethermochromic temperature range of the system. These formulations forman internal phase that is then microencapsulated within a polymericshell. The microcapsules are referred to as thermochromic pigment.

The processing outlined below may be used to produce microcapsules ofmuch smaller dimensions than are obtainable from the prior art. By wayof example, these smaller capsules may have an average particle diameterthat ranges from 400 nm to 1.5 microns. In fact, substantially allparticles, such as more than 95% or more than 90% of all particles, maybe smaller than 1.5 microns. If necessary, larger particles resultingfrom the process may be removed by labyrinth or depth filters. Thisresults in particle size distributions that are substantially smallerthan the smallest distributions obtainable from the prior art.

As shown in FIG. 4, process 400 utilizes unique chemistry to produce areactive pigment that may be dispersed in a polyester resin ink vehicle.An emulsion mixture used to form the microcapsules may be formulated aspremixtures in three parts.

Step 402 entails mixing an emulsifier into an aqueous solution thatcontains water and optionally other polar solvents that are misciblewith water. Water is the preferred solvent. This is mixed to substantialhomogeneity with a surfactant material that is used as an emulsifier oremulsion stabilizer. The emulsifier may suitably include, for example,nonionic, anionic, cationic, or zwitterionic surfactants, polymers orcopolymers, or reactive diluents such as aliphatic or cycloaliphaticglycidyl ethers. Anionic surfactants are preferred. The art sometimesrefers to these materials as anionic protective colloids. These are usedto disperse fine droplets of hydrophobic liquid in an aqueous medium,for keeping the dispersed droplets from aggregation or unification.Useful materials for the formation of anionic protective colloids forsuch a purpose are anionic polymers, which are exemplified bypolystyrenesulfonate, styrene copolymers, polyvinylsulfonatester salts,polyvinylsulfonates, maleic anhydridestyrene copolymer, maleicanhydride-isobutylene copolymer, maleic anhydride-ethylene copolymer,maleic anhydride-methyl vinyl ether copolymer, polyvinyl alcohol(saponified product), carboxymethyl-modified polyvinyl alcohol, gumarabic, polyacrylates, polyacrylate derivatives, acrylate copolymers,carboxymethyl cellulose, gelatin, pectin, pullulan, phtahalated gelatin,succinated gelatin, other gelatin derivatives, cellulose sulfate estersalt, and alginic acid.

The anionic emulsifiers are particularly preferred. By way of example,the anionic emulsifier ethylene maleic anhydride (EMA) is suitably used,as are homologues of EMA. These materials may be pH adjusted using anamine, such as triethanolamine. For example, one useful surfactantmaterial is hydrolyzed ethylene maleic anhydride adjusted to a pH ofaround 4.0 with triethnolamine. This first premixture according to step402 preferably constitutes from 40% to 70% by weight of the finalemulsion mixture, with about 50% w/w being used in a working examplebelow. From 1% to 10% by weight of the aqueous solution suitablycontains an anionic surfactant used as the emulsifier, with significantreductions in particle size being obtainable when the amount ofsurfactant provided is sufficient to impart more than 2% by weight ofthe surfactant in the final emulsion slurry where microencapsulation isto be performed. The amount of anionic surfactant in this final slurryis preferably from 2% to 7% by weight, with from 2.3% to 6% being morepreferred and 2.5% to 5% being even more preferred and 2.5% to 3% beingmost preferred. Water may comprise the balance of the aqueous solution.

Step 404 entails mixing an internal phase mixture that constitutes anyof the internal phase materials described below and is generallyinsoluble with the aqueous phase. These materials are combined to formthermochromic systems using ratios of ingredients as are known in theart. Although there may be additional additives as described below, theessential internal phase components include a leuco dye, a developer forthe leuco dye, and a carrier such as a microcrystalline wax which mayalternatively be an ester, ketone, and/or alcohol. The internal phasemixture constitutes from 23% to 35% by weight of the emulsion mixture,with 30% by weight being used in a working example below.

Step 406 entails preparing an amine-formaldehyde resin solution. This ispreferably of the class known as having high amine content, as thisincreases solubility of the resin in water. This is mixed with water oranother compatible polar solvent, preferably in an amount where thewater ranges from 40% to 60% of the amine formaldehyde resin solution.The amine formaldehyde solution preferably constitutes from 15% to 28%by weight of the emulsion mixture or slurry, with 20% being used in aworking example below.

The foregoing premixtures are maintained 408 at respective temperatureprofiles to facilitate further mixing under conditions of high shearmixing. The aqueous solution is maintained at a temperature ranging from70° C. to 80° C. For example, this may be done in a reaction vessel thatis jacketed for temperature control. The amine-formaldehyde resinsolution is maintained at a temperature ranging from 20° C. to 50° C.The internal phase mixture including leuco dye, developer, and carrieris maintained at a temperature of 120° C. to 130° C., or anothertemperature as may be required as is sufficient to liquefy the carrier.

The respective solutions are blended 410 to form an emulsion. In apreferred mixing order, the internal phase solution is poured into theaqueous solution under high shear conditions created by a homogenizer,such as a rotor/stator that is submerged in the emulsification solution.The entire volume of the internal phase is introduced under a controlledtimed pour based on batch size. The high shear homogenizer runs untilthe internal phase produces an oil-in-water emulsion that facilitatesparticle sizes of the desired distribution. Once the emulsion isgenerated, the amine-formaldehyde solution is poured under a controlledtime condition while the homogenizer rapidly disperses the wall formingpre-polymer. At the end of the resin addition, the homogenizer is shutdown and removed from the process. A large impeller type mixer is thenengaged in the slurry to keep the capsules suspended while the capsulewalls form. This is done while maintaining a temperature of 70° C. to90° C., most preferably 80° C.

Once a stable emulsion of the desired particle size is created while thepolymer wall is forming, a catalyst for polymerizing the resin isoptionally added 412. The resin may be combined with one or more knowncatalysts to initiate polymerization. Certain curing agents may be addedto quicken the cure rate of the amine formaldehyde resin withoutpermanently activating the thermochromic system.

Suitable cure accelerators or catalysts include, but are not limited to,imidazoles, amidoamines, linear phenolics, blocked and unblocked acidcatalysts, isocyanates, dihydrazides or photoinitiators anddodecylbenzenesulfonic acid. In one preferred embodiment, the curingagent is dodecylbenzenesulfonic acid. Suitable curing agents include atleast the following acid catalyst curing agents, for example: A 40S; ABS100; Ambicat LE 4476; B 121; B 121 (also a surfactant); Bio-Soft S 100;Bio-Soft S 101; Biosoft S 126; Calsoft LAS 99; Cat 6000; Catalyst 600;Catalyst 6000; Cycat 600; DBS; Dobanic acid; Dodecylbenzenesulphonicacid; E 7256; Elfan WA Sulphonic Acid; LAS 99; laurylbenzenesulfonicacid; Lipon LH 500; Maranil DBS; Marlon AS 3; Nacconol 98SA; Nacure5074; Nacure 5076; Nansa 1042; Nansa 1042P; Nansa SSA; Neopelex FS;Neopelex GS; Neopelex GS-P; P 3 Vetralat; Pelex F 25; Polystep A 13;Rhodacal SSA/A; Richonic Acid B; S 100; Soft Osen 5S; Sulfosoft;Sulframin 1298; Sulframin Acid 1298; Taycacure AC 430; Taycapower L120D; Taycapower L 121; Taycapower L 122; Ufacid K; Witco 1298; Witco1298 Acid Soft; Witco 1298 Soft Acid; Witconic 1298 Hard Acid; Witconic1298 Soft Acid; blocked or unblocked acid catalysts; Decotherm 255e,Nacure 2500, cycat 4040, cycat 4045, cycat 600, paratoluene sulfonicacid, amine blocked paratoluenesulfonic acid; andn-dodecylbenzenesulfonic acid. For small microcapsules, p-toluenesulfonic acid catalysts are particularly preferred, and amine-blockedp-toluene sulfonic acid catalysts are especially preferred.

In the case of a toluene sulfonic acid catalyst, this is added at 5% to30% by weight of the amine formaldehyde resin. The pH is adjusted toabout 4 by addition of an amine, such as triethnolamine. Under the hightemperature and low pH, the amine formaldehyde resin will polymerize andaccumulate as the capsule wall around the internal phase. The resin wallwill further crosslink into a hardened shell over a period of 2-8 hourswhile the polymerization reaction occurs at a temperature from 80° C. to90° C. The use of an amine blocked toluene sulfonic acid enhances thecapsule wall density making the microcapsules more chemically resistant.

At this time, a stabilizing agent is optionally added 414. Thestabilizing agent may be a metallocene catalyst or transition metalbonded to organic moieties through oxygen linkages. Preferred forms ofthe stabilizing agent are transition metal soaps, or any othercarboxylic acid salt including a catalytic metal-oxygen moiety. Theorganic tail of these preferred materials improves solubility anddispersion. Zirconium 2-ethylhexanoate is particularly preferred. Thisadditive interacts with the surface of the polymerized microcapsules toprotect the thermochromic functionality thereof when the pigment ismixed with inks or coatings. In one aspect, Formula (1) below shows thestructure of a carboxylate salt that may be used as described herein:

M^(n)(R)n;

where M is a metal as described above of oxidation state n; and R is acarboxylate having a carbon number ranging from five to fourteen. M ispreferably a transition metal. R is preferably a branched derivative ofhexanoic acid, such as 2-ethyl hexanoate.

In another aspect, a metallocene catalyst may be provided withtransition metals bonded to oxygen, nitrogen, and/or halogen atoms.

After polymerization, the slurry will have a high kinematic viscosityranging from 2000 to 4000 centipoise. The slurry is approximately 40% byweight solids including capsules and other materials, together withapproximately 60% water. In order to produce a metal decoration ink, thebulk of the water needs to be removed from the liquid slurry, thusreducing the amount of water from 60% by weight percentage to apercentage of from 20%-40% by weight.

The dewatering step 416 is accomplished by filtering the slurry using amesh filter. This may be facilitated by positive pressure or undervacuum, as well as by chemical additives as are known in the art.Further dewatering may be accomplished by introducing the filteredslurry into a jacketed vacuum mixer which will maintain a hightemperature under vacuum with continuous mixing.

The final dewatered pigment is then suitable for processing into a metaldecorating ink that can withstand a high temperature oven cure withoutextreme color loss, and will also have improved transfer rheologywithout severe misting. The resulting pigment may be mixed with avehicle 418 to form a coating or ink for printing. This may be used 420in canning or printing operations, or any other application forthermochromic pigments.

The discussion that follows describes a variety of materials which areuseful in the forgoing process.

Internal Phase Components *Photochromic Dyes

Photochromic dyes may be used as the internal phase. Known classes ofphotochromic dyes include, without limitation, spiropyrans,spirooxazines diarylethenes, azobenzenes, and photochromic quinones.

*Leuco Dyes

Leuco dyes most commonly used as color formers in thermochromic systemsof the present disclosure include, but are not limited to, generally;spirolactones, fluorans, spiropyrans, and fulgides; and morespecifically; diphenylmethane phthalide derivatives,phenylindolylphthalide derivatives, indolylphthalide derivatives,diphenylmethane azaphthalide derivatives, phenylindolylazaphthalidederivatives, fluoran derivatives, styrynoquinoline derivatives, anddiaza-rhodamine lactone derivatives which can include:3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide;3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl) phthalide;3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide;3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide;3-[2-ethoxy-4-(N-ethylanilino)phenyl]-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide;3,6-dimethoxyfluoran; 3,6-di-n-butoxyfluoran;2-methyl-6-(N-ethyl-N-p-tolylamino)fluoran;3-chloro-6-cyclohexylaminofluoran; 2-methyl-6-cyclohexylaminofluoran;2-(2-chloroanilino)-6-di-n-butylamino fluoran;2-(3-trifluoromethylanilino)-6-diethylaminofluoran;2-(N-methylanilino)-6-(N-ethyl-N-p-tolylamino) fluoran,1,3-dimethyl-6-diethylaminofluoran; 2-chloro-3-methyl-6-diethylaminofluoran; 2-anilino-3-methyl-6-diethylaminofluoran;2-anilino-3-methyl-6-di-n-butylamino fluoran;2-xylidino-3-methyl-6-diethylaminofluoran;1,2-benzo-6-diethylaminofluoran;1,2-benzo-6-(N-ethyl-N-isobutylamino)fluoran,1,2-benzo-6-(N-ethyl-N-isoamylamino)fluoran;2-(3-methoxy-4-dodecoxystyryl)quinoline; spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one;2-(diethylamino)-8-(diethylamino)-4-methyl-spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one;2-(di-n-butylamino)-8-(di-n-butylamino)-4-methyl-spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one;2-(di-n-butylamino)-8-(diethylamino)-4-methyl-spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one;2-(di-n-butylamino)-8(N-ethyl-N-isoamylamino)-4-methyl-spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one; and2-(di-n-butylamino)-8-(di-n-butylamino)-4-phenyl and trisubstitutedpyridines.

Particularly preferred materials for use as chromatic compounds are ofdiphenylmethane phthalide derivatives, phenylindolylphthalidederivatives, indolylphthalide derivatives, diphenylmethane azaphthalidederivatives, phenylindolylazaphthalide derivatives, fluoran derivatives,styrynoquinoline derivatives, 2,4,6, trisubstituted pyridines,quinazolines, bis-quinazolines, and diaza-rhodamine lactone derivatives,in any combination.

Specific examples of 2,4,6 trisubstituted pyridine dyes are described indetail in copending U.S. patent application Ser. No. 61/542,738 filedOct. 3, 2011, which is hereby incorporated by reference to the sameextent as though fully replicated herein. Compounds 1-45 below are dyesthat exemplify these materials and may be used in any combination.

-   4,4′-dialkyl-2,2′-biphenol,-   4,4′-dichloro, difluoro, dibromo, diiodo-2,2′-biphenol,-   4,4′-dicarboalkoxy-2,2′-biphenol, and-   4,4′-diacetyl, dibenzoyl-2,2′-biphenol and 5-alkyl-salicylic acid.

*Developers

Weak acids that can be used as color developers act as proton donors,changing the dye molecule between its leuco form and its protonatedcolored form; stronger acids make the change irreversible. Examples ofdevelopers used in the present disclosure include but are not limitedto: bisphenol A; bisphenol F; tetrabromobisphenol A;1′-methylenedi-2-naphthol; 1,1,1-tris(4-hydroxyphenyl)ethane;1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane;1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;1,1-bis(4-hydroxyphenyl)cyclohexane;1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene; 1-naphthol; 2-naphthol;2,2 bis(2-hydroxy-5-biphenylyl)propane;2,2-bis(3-cyclohexyl-4-hydroxy)propane;2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane;2,2-bis(4-hydroxy-3-isopropylphenyl)propane;2,2-bis(4-hydroxy-3-methylphenyl)propane;2,2-bis(4-hydroxyphenyl)propane; 2,3,4-trihydroxydiphenylmethane;4,4′-(1,3-Dimethylbutylidene)diphenol; 4,4′-(2-Ethylidene)diphenol;4,4′-(2-hydroxybenzylidene)bis(2,3,6-trimethylphenol); 4,4′-biphenol;4,4′-dihydroxydiphenyl ether; 4,4′-dihydroxydiphenylmethane;4,4′-methylidenebis(2-methylphenol); 4-(1,1,3,3-tetramethylbutyl)phenol;4-phenylphenol; 4-tert-butylphenol; 9,9-bis(4-hydroxyphenyl)fluorine;4,4′-(ethane-1,1-diyl)diphenol;alpha,alpha′-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene;alpha,alpha,alpha′-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene;benzyl 4-hydroxybenzoate; bis(4-hydroxyphenyl) sulfide;bis(4-hydroxyphenyl)sulfone; propyl 4-hydroxybenzoate; methyl4-hydroxybenzoate; resorcinol; 4-tert-butyl-catechol;4-tert-butyl-benzoic acid; 1,1′-methylenedi-2-naphthol1,1,1-tris(4-hydroxyphenyl)ethane;1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane;1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;1,1-bis(4-hydroxyphenyl)cyclohexane;1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene; 1-naphthol 2,2′-biphenol;2,2-bis(2-hydroxy-5-biphenylyl)propane;2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane;2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane;2,2-bis(4-hydroxy-3-isopropylphenyl)propane;2,2-bis(4-hydroxy-3-methylphenyl)propane;2,2-bis(4-hydroxyphenyl)propane; 2,3,4-trihydroxydiphenylmethane;2-naphthol; 4,4′-(1,3-dimethylbutylidene)diphenol;4,4′-(2-ethylhexylidene)diphenol4,4′-(2-hydroxybenzylidene)bis(2,3,6-trimethylphenol); 4,4′-biphenol;4,4′-dihydroxydiphenyl ether; 4,4′-dihydroxydiphenylmethane;4,4′-ethylidenebisphenol; 4,4′-methylenebis(2-methylphenol);4-(1,1,3,3-tetramethylbutyl)phenol; 4-phenylphenol; 4-tert-butylphenol;9,9-bis(4-hydroxyphenyl)fluorine;alpha,alpha′-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene;α,α,α-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene; benzyl4-hydroxybenzoate; bis(4-hydroxyphenyl) sulfidem; bis(4-hydroxyphenyl)sulfone methyl 4-hydroxybenzoate; resorcinol; tetrabromobisphenol A;derivative salts of salicylic acid such as 3,5-di-tertbutyl-salicylicacid; zinc 3,5-di-tertbutylsalicylate; 3-phenyl-salicylic acid;5-tertbutyl-salicylic acid; 5-n-octyl-salicylic acid; 2,2′-biphenol;4,4′-di-tertbutyl-2,2′-biphenol; 4,4′-di-n-alkyl-2,2′-biphenol; and4,4′-di-halo-2,2′-biphenol, wherein the halo is chloro, fluoro, bromo,or iodo.

Specific examples of known leuco dye developers are shown below:

The leuco dyes are combined with leuco dye developers for makingthermochromic compositions. These materials are found to generateabsorption densities from the leuco dyes when formulated with a carrierthat contains one or more fatty ester, fatty alcohol, and fatty amide.The combination of leuco dyes, developers and carrier materials may beused in any combination to achieve the listed functionalities. By way ofexample, this combination of molecules includes any combination of thefollowing molecules: bipyridyl and terpyridine leuco dyes of the type2-[2-pyridyl]-6-phenyl-4-dialkylamino-pyridine,2-[2-pyridyl]-6-phenyl-4-diarylamino-pyridine,2-[2-pyridyl]-6-phenyl-4-hydroxy-pyridine,2-[2-pyridyl]-6-[2-pyridyl]-4-dialkylamino-pyridine,2-[2-pyridyl]-6-[2-pyridyl]-4-diarylamino-pyridine,2-[2-pyridyl]-6-[2-pyridyl]-4-hydroxy-pyridine, molecules from FIG. 3including at least the following; 26, 27, 29, 30, 31, 32, 33, 34, 35,36, 38, 39, 41, 42, and 43; also 2,6-diphenyl-4-dialkylamino-pyridines,2,6-diphenyl-4-diarylamino-pyridines, 2,6-diphenyl-4-hydroxy-pyridines,2,6-diphenyl-4-alkoxy-pyridines, 2,6-diphenyl-4-aryloxy-pyridines,molecules from FIG. 3 including at least the following; 1, 3, 5, 6, 7,8, 9, 10, 13, 17, 19, 20, 21, 22, 23, 24; and4,4′-dialkyl-2,2′-biphenol, 4,4′-dichloro, difluoro, dibromo,diiodo-2,2′-biphenol, 4,4′-dicarboalkoxy-2,2′-biphenol, 4,4′-diacetyl,dibenzoyl-2,2′-biphenol as well as salicylic acids including at least5-alkyl-salicylic acid.

Furthermore the composition so obtained may be encapsulated in aseparate composition, such as a melamine-formaldehyde resin, to produceabsorption changing pigments designed for use in formulated ink andcoating products as well as plastic pellet concentrates for injectionmolded or extruded plastic products.

Some materials function as both leuco dyes and light absorbers:

Visible Range Absorbers (400 nm to 700 nm):

-   4-(4′-dimethylamino-phenyl)-2,6-diphenyl-pyridine (dye 11)-   4-(4′-diphenylamino-phenyl)-2,6-diphenyl-pyridine (dye 3)

Near UVA Range Absorbers:

-   4-(4-ethoxy-phenyl)-2,6-diphenyl-pyridine (dye 1).-   4-(4-phenoxy-phenyl)-2,6-diphenyl-pyridine (dye 3).

These developers are particularly preferred for use with the 2,4,6tri-substituted pyridine dyes

*Carriers/Solvents for the Internal Phase

The best solvents to use within the thermochromic system are those thathave low reactivity, have a relatively large molecular weight (i.e. over100), and which are relatively non-polar. Ketones, diols and aromaticcompounds should not be used as solvents within the internal phase orthermochromic system.

Solvents and/or co-solvents used in thermochromic systems generally mayinclude, but are not limited to: aldehydes, thiols, sulfides, ethers,ketones, esters, alcohols, and acid amides. These solvents can be usedalone or in mixtures of 2 or more. Examples of the sulfides include, butare not limited to: di-n-octyl sulfide; di-n-nonyl sulfide; di-n-decylsulfide; di-n-dodecyl sulfide; di-n-tetradecyl sulfide; di-n-hexadecylsulfide; di-n-octadecyl sulfide; octyl dodecyl sulfide; diphenylsulfide; dibenzyl sulfide; ditolyl sulfide; diethylphenyl sulfide;dinaphthyl sulfide; 4,4′-dichlorodiphenyl sulfide; and2,4,5,4′tetrachlorodiphenyl sulfide. Examples of the ethers include, butare not limited to: aliphatic ethers having 10 or more carbon atoms,such as dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether,dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether,ditridecyl ether, ditetradecyl ether, dipentadecyl ether, dihexadecylether, dioctadecyl ether, decanediol dimethyl ether, undecanedioldimethyl ether, dodecanediol dimethyl ether, tridecanediol dimethylether, decanediol diethyl ether, and undecanediol diethyl ether;alicyclic ethers such as s-trioxane; and aromatic ethers such asphenylether, benzyl phenyl ether, dibenzyl ether, di-p-tolyl ether,1-methoxynaphthalene, and 3,4,5trimethoxytoluene.

Examples of ketone solvents include, but are not limited to: aliphaticketones having 10 or more carbon atoms, such as 2-decanone, 3-decanone,4-decanone, 2-undecanone, 3-undecanone, 4-undecanone, 5-undecanone,6-undecanone, 2-dodecanone, 3-dodecanone, 4-dodecanone, 5-dodecanone,2-tridecanone, 3-tridecanone, 2-tetradecanone, 2-pentadecanone,8-pentadecanone, 2-hexadecanone, 3-hexadecanone, 9-heptadecanone,2-pentadecanone, 2-octadecanone, 2-nonadecanone, 10-nonadecanone,2-eicosanone, 11-eicosanone, 2-heneicosanone, 2-docosanone, laurone, andstearone; aryl alkyl ketones having 12 to 24 carbon atoms, such asn-octadecanophenone, n-heptadecanophenone, n-hexadecanophenone,n-pentadecanophenone, n-tetradecanophenone, 4-n-dodecaacetophenone,n-tridecanophenone, 4-n-undecanoacetophenone, n-laurophenone,4-n-decanoacetophenone, n-undecanophenone, 4-n-nonylacetophenone,n-decanophenone, 4-n-octylacetophenone, n-nonanophenone,4-n-heptylacetophenone, n-octanophenone, 4-n-hexylacetophenone,4-n-cyclohexylacetophenone, 4-tert-butylpropiophenone, n-heptaphenone,4-n-pentylacetophenone, cyclohexyl phenyl ketone, benzyl n-butyl ketone,4-n-butylacetophenone, n-hexanophenone, 4-isobutylacetophenone,1-acetonaphthone, 2-acetonaphthone, and cyclopentyl phenyl ketone; arylaryl ketones such as benzophenone, benzyl phenyl ketone, and dibenzylketone; and alicyclic ketones such as cyclooctanone, cyclododecanone,cyclopentadecanone, and 4-tert-butylcyclohexanone, ethyl caprylate,octyl caprylate, stearyl caprylate, myristyl caprate, stearyl caprate,docosyl caprate, 2-ethylhexyl laurate, n-decyl laurate, 3-methylbutylmyristate, cetyl myristate, isopropyl palmitate, neopentyl palmitate,nonyl palmitate, cyclohexyl palmitate, n-butyl stearate, 2-methylbutylstearate, stearyl behenate 3,5,5-trimethylhexyl stearate, n-undecylstearate, pentadecyl stearate, stearyl stearate, cyclohexylmethylstearate, isopropyl behenate, hexyl behenate, lauryl behenate, behenylbehenate, cetyl benzoate, stearyl p-tert-butylbenzoate, dimyristylphthalate, distearyl phthalate, dimyristyl oxalate, dicetyl oxalate,dicetyl malonate, dilauryl succinate, dilauryl glutarate, diundecyladipate, dilauryl azelate, di-n-nonyl sebacate,1,18-dineopentyloctadecylmethylenedicarboxylate, ethylene glycoldimyristate, propylene glycol dilaurate, propylene glycol distearate,hexylene glycol dipalmitate, 1,5-pentanediol dimyristate,1,2,6-hexanetriol trimyristate, 1,4-cyclohexanediol didecanoate,1,4-cyclohexanedimethanol dimyristate, xylene glycol dicaprate, andxylene glycol distearate.

Without limitation, ester solvents may be selected from esters of asaturated fatty acid with a branched aliphatic alcohol, esters of anunsaturated fatty acid or a saturated fatty acid having one or morebranches or substituents with an aliphatic alcohol having one or morebranches or 16 or more carbon atoms, cetyl butyrate, stearyl butyrate,and behenyl butyrate including 2-ethylhexyl butyrate, 2-ethylhexylbehenate, 2-ethylhexyl myristate, 2-ethylhexyl caprate,3,5,5-trimethylhexyl laurate, butyl palmitate, 3,5,5-trimethylhexylpalmitate, 3,5,5-trimethylhexyl stearate, 2-methylbutyl caproate,2-methylbutyl caprylate, 2-methylbutyl caprate, 1-ethylpropyl palmitate,1-ethylpropyl stearate, 1-ethylpropyl behenate, 1-ethylhexyl laurate,1-ethylhexyl myristate, 1-ethylhexyl palmitate, 2-methylpentyl caproate,2-methylpentyl caprylate, 2-methylpentyl caprate, 2-methylpentyllaurate, 2-methylbutyl stearate, 2-methylbutyl stearate, 3-methylbutylstearate, 2-methylheptyl stearate, 2-methylbutyl behenate, 3-methylbutylbehenate, 1-methylheptyl stearate, 1-methylheptyl behenate,1-ethylpentyl caproate, 1-ethylpentyl palmitate, 1-methylpropylstearate, 1-methyloctyl stearate, 1-methylhexyl stearate,1,1dimethylpropyl laurate, 1-methylpentyl caprate, 2-methylhexylpalmitate, 2-methylhexyl stearate, 2-methylhexyl behenate,3,7-dimethyloctyl laurate, 3,7-dimethyloctyl myristate,3,7-dimethyloctyl palmitate, 3,7-dimethyloctyl stearate,3,7-dimethyloctyl behenate, stearyl oleate, behenyl oleate, stearyllinoleate, behenyl linoleate, 3,7-dimethyloctyl erucate, stearylerucate, isostearyl erucate, cetyl isostearate, stearyl isostearate,2-methylpentyl 12-hydroxystearate, 2-ethylhexyl 18-bromostearate,isostearyl 2-ketomyristate, 2-ethylhexyl-2-fluoromyristate, cetylbutyrate, stearyl butyrate, and behenyl butyrate.

Examples of the alcohol solvents include, without limitation, monohydricaliphatic saturated alcohols such as decyl alcohol, undecyl alcohol,dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecylalcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol,eicosyl alcohol, behenyl alcohol and docosyl alcohol; aliphaticunsaturated alcohols such as allyl alcohol and oleyl alcohol, alicyclicalcohols such as cyclopentanol, cyclohexanol, cyclooctanol,cyclododecanol, and 4-tert-butylcyclohexanol; aromatic alcohols such as4-methylbenzyl alcohol and benzhydrol; and polyhydric alcohols such aspolyethylene glycol. Examples of the acid amides include, but are notlimited to: acetamide, propionamide, butyramide, capronamide,caprylamide, capric amide, lauramide, myristamide, palmitamide,stearamide, behenamide, oleamide, erucamide, benzamide, capronanilide,caprylanilide, capric anilide, lauranilide, myristanilide,palmitanilide, stearanilide, behenanilide, oleanilide, erucanilide,N-methylcapronamide, N-methylcaprylamide, N-methyl (capric amide),N-methyllauramide, N-methylmyristamide, N-methylpalmitamide,N-methylstearamide, N-methylbehenamide, N-methyloleamide,N-methylerucamide, N-ethyllauramide, N-ethylmyristamide,N-ethylpalmitamide, N-ethylstearamide, N-ethyloleamide,N-butyllauramide, N-butylmyristamide, N-butylpalmitamide,N-butylstearamide, N-butyloleamide, N-octyllauramide,N-octylmyristamide, N-octylpalmitamide, N-octylstearamide,N-octyloleamide, N-dodecyllauramide, N-dodecylmyristamide,N-dodecylpalmitamide, N-dodecylstearamide, N-dodecyloleamide,dilauroylamine, dimyristoylamine, dipalmitoylamine, distearoylamine,dioleoylamine, trilauroylamine, trimyristoylamine, tripalmitoylamine,tristearoylamine, trioleoylamine, succinamide, adipamide, glutaramide,malonamide, azelamide, maleamide, N-methylsuccinamide, N-methyladipamide, N-methylglutaramide, N-methylmalonamide, N-methylazelamide,N-ethylsuccinamide, N-ethyladipamide, N-ethylglutaramide,N-ethylmalonamide, N-ethylazelamide, N-butylsuccinamide,N-butyladipamide, N-butylglutaramide, N-butylmalonamide,N-octyladipamide, and N-dodecyladipamide.

Certain solvents reduce the hysteresis window. The solvent may bematerial combined with the thermochromic system, for example, to reducethermal separation across the hysteresis window to a level demonstrating80%, 70%, 50%, 40%, 30% or less of the thermal separation that wouldexist if the co-solvent were not present. The co-solvent is selectedfrom the group consisting of derivatives of mysristic acid, derivativesof behenyl acid, derivatives of palmytic acid and combinations thereof.Generally, these materials include myristates, palmitates, behenates,together with myristyl, stearyl, and behenyl materials and certainalcohols. In one aspect, these materials are preferably solvents andco-solvents from the group including isopropyl myristate, isopropylpalmitate, methyl palmitate, methyl stearate, myristyl myristate, cetylalcohol, stearyl alcohol, behenyl alcohol, stearyl behenate, andstearamide. These co-solvents are added to the encapsulatedthermochromic system in an amount that, for example, ranges from 9% to18% by weight of the thermochromic system as encapsulated, i.e.,excluding the weight of the capsule. This range is more preferably fromabout 12% to about 15% by weight.

*Light Stabilizers

In other instances, additives used to fortify the encapsulatedthermochromic systems by imparting a resistance to degradation byultraviolet light by having a dual functionality of also reducing thewidth of separation over the hysteresis window. Light stabilizers areadditives which prevent degradation of a product due to exposure toultraviolet radiation. These compounds may include blocked phenols,singlet oxygen quenchers, UVA/B absorbers, borotriazoles, and hinderedamino light stabilizers (HALS). Specific examples of light stabilizersused in thermochromic systems of the present disclosure and which mayalso influence the hysteresis window include but are not limited to:avobenzone, bisdisulizole disodium, diethylaminohydroxybenzoyl hexylbenzoate, Ecamsule, methyl anthranilate, 4-aminobenzoic acid, Cinoxate,ethylhexyl triazone, homosalate, 4-methylbenzylidene camphor, octylmethoxycinnamate, octyl salicylate, Padimate O, phenylbenzimidazolesulfonic acid, polysilicone-15, trolamine salicylate, bemotrizinol,benzophenones 1-12, dioxybenzone, drometrizole trisiloxane,iscotrizinol, octocrylene,tetrakis-(methylene-(3,5-di-(tert)-butyl-4-hydrocinnamate)) methane,oxybenzone, sulisobenzone, bisoctrizole, titanium dioxide, zinc oxide,and sterically hindrered phenols such as pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate sold asIrganox 1010® by Ciba Specialty Chemicals Inc. of Tarrytown N.Y.

Ink Formulations

The encapsulated thermochromic systems of the present disclosure may bereferred to as pigments. In an embodiment of the present disclosure, thepigments are used in formulating photochromic or thermochromic dyes,inks or coatings. In order to add normal pigment to ink, dye, orlacquer, the pigment itself is ground under high shear into the base.This disperses the pigment throughout the base. Since the pigment isusually a solid crystal with a diameter approximating one micron, thisgrinding is not difficult to do. The eye cannot see particles that size,so the pigment will give the base a solid color. The addition of morepigment intensifies the color. Since the pigment has a very intensecolor only about 10% of the final ink is made up of normal pigments.

A base for an ink formulation using encapsulated thermochromic systemsof the present disclosure may be developed using off the shelfingredients. The ink will incorporate, where possible, and be compatiblewith different ink types and solvents with molecular weights larger than100 while avoiding low molecular weight aldehydes, diols, alcohols,ketones, and, in general, aromatic compounds. Important considerationswith respect to the ingredients within the ink vehicle are thereactivity of the ingredients with the encapsulated thermochromicsystem.

An example of unwanted interactions between media and the encapsulatedthermochromic systems can occur between compounds found in inkformulations. The long alkyl chains of many of the compounds found inink vehicles may have reactive portions that can fit through the poresof the capsule and interact with the inner phase and denature it throughthis interaction. Since the behavior of the thermochromic system isrelated to the shape and the location of its molecules at giventemperatures, disrupting these structures could have a large impact onthe characteristics of the thermochromic system. Even molecules thatcannot fit through the capsule pores may have reactive portions thatcould protrude into the capsule and thereby influence the colortransition of the thermochromic system within the capsule. Therefore,ammonia, short chain mineral spirits, acids, ketones, diols, alcohols,ethers and aldehydes are preferably minimized in any medium in which themicroencapsulated pigments are also present. If these compounds aresubstantially reduced or eliminated the thermochromic systems willperform better and have a longer shelf life.

Another step in using the encapsulated thermochromic systems of thepresent disclosure in ink formulations is to adjust the pH or lower theacid value of the ink base before the thermochromic system is added.This can be done by ensuring that each individual component of the baseis at the correct pH or acid value or by simply adding a proton donor orproton acceptor to the base itself prior to adding the thermochromicsystem. The appropriate specific pH is generally neutral, or 7.0. The pHwill vary between 6.0 and 8.0 depending on the ink type and the colorand batch of the thermochromic system.

Once a slurry and the base have been properly prepared, they arecombined. The method of stirring should be low speed with non-metal stirblades and other manufacturing equipment known to those skilled in theart of ink making. Other additives may be incorporated to keep thethermochromic system suspended. The ink should be stored at or slightlybelow room temperature.

Most thermochromic inks or coatings undergo a color change from aspecific color to colorless. Therefore, layers of background colors canbe provided under thermochromic layers that will only be seen when thethermochromic layer changes to colorless. Alternatively, a base colormay be added to the thermochromic ink or coating, such that thebackground color is that of the base color, as opposed to beingcolorless. If an undercoat of yellow is applied to the substrate andthen a layer containing blue thermochromic dye is applied the color willappear to change from green to yellow, when what is really happening isthat the blue is changing to colorless.

Where the pigment is photochromic in nature, it will be appreciated alsothat a base color may be added to the photochromic inks or coatings.Multichromatic inks or coatings may be made by combining photochromicand thermochromic materials. This may be done by mixing thermochromicpigments and photochromic materials that have been separatelymicroencapsulated, or else the photochromic dye and thermochromic dye(together with other additives) may be combined for use in the internalphase at the time of microencapsulation.

In an embodiment, thermochromic systems of the present disclosureformulated as dyes or inks may be used for the printing ofidentification or forgery detection marks or patterns on securitydocuments. These inks may also be used simultaneously with conventionalprinting inks and also may be used with pre-existing printers bysubstitution with one of the normally used printing inks.

In one embodiment, a thermochromic coating formulation includes:

Weight Percent Ingredient of Coating Pigment* 1% to 40% VehiclePolymerizable resin 5% to 30% Dispersing agent 0% to 5% Solvent 0% to50% Curing agent 0% to 25% Wax 0% to 5% *Assessed by solids content uponcomplete drying of pigment capsules, but does not need to be dried andmay be mixed as a slurry.

In one aspect, a reversible thermochromic coating for use in can andcoil coatings contains a reversible thermochromic pigment in an amountfrom 1% to 40% by weight of the coating, and a vehicle forming thebalance of the coating. The vehicle includes a resin selected from thegroup consisting of epoxy, polyester, urethane, acrylic acid andacrylate resins, and combinations thereof. Commercially availablethermochromic systems may be readily obtained in a variety of colorsdemonstrating color transition temperatures from about minus 5° C. andup to about 65° C. A range of color formulations may be made by mixingthe pigment to include one or more of the following reversiblethermochromic colors: yellow, magenta, cyan, and black. These may befurther mixed to include other dyes or solid pigments that arenon-thermochromic in nature. The pigment may change from a colorlessstate to a colored state upon cooling to the reactive temperature, or toa colored state upon heating to the reactive temperature. It ispreferred that the microcapsules are formed of urea-formaldehyde ormelamine-formaldehyde that is acid catalyzed to enhance the inherentstability in polar, low molecular weight solvents having a molecularweight of about less than 100 g/mol.

When premixed using a nonpolar solvent, the coatings can demonstrateshelf stability exceeding 14 to 45 days when stored at about 20° C. Somecoating formulations demonstrate shelf stability in excess of one year.

The curing agent is generally compatible with the resin for this purposeand may be, for example, a latent blocked amine to initiate apolymerization reaction upon heating.

The coating may be roller-coated onto coil stock aluminum or steel andthe roll stock aluminum is subsequently formed into one or more beveragecan components. These components may be selected from the groupconsisting of beverage can ends, beverage can tabs, bottle caps, and/orbeverage container closures. The aluminum is preferably an alloy that iscommonly used in canning operations, such as aluminum alloy 5182-H48.The coatings work well also on other metals including, withoutlimitation, steel and plate steel. The coating process preferably occursin one or more coats to yield a dried film with a thickness ranging from1 mg/in² up to 5.5 mg/in².

Additional applications include using the microencapsulated pigmentsdescribed herein as chromophores in otherwise conventional formulationsfor:

Coil metal coatings;

Inkjet inks;

Metal decoration inks;

End printing coatings for use in beverage cans;

Coatings for printing on the crowns of beverage cans;

Coatings for printing on closures of beverage cans, such as screw-oncaps;

Coatings used in web offset printing;

Screen printing inks and coatings;

Solvent based inks and coatings;

Water based inks and coatings;

Oxidation cure coatings;

UV cure coatings;

Electron-beam cured coatings; and

Master batch epoxy coatings in either one part or two part systems.

The various embodiments shown below are nonlimiting in nature, teachingby way of example and not by limitation.

Working Example 1 Large Batch Slurry Process for Small ParticleMicrocapsules Sample Batch Formulation:

Color: Batch 60.00 KG Size: Green Date: Material %/Amount (Kg) EMA 50%30.0 KG 2-7%- EMA in final slurry Total IP 30% 18.0 KG Internal 50%Alcohol / Phase Ester Color former 1-10% Leuco Dye Developer 5-30%phenolic developer Additional Additive toluene 5-30% by (curing agent)sulfonic weight of the acid amine catalyst formaldehyde resin.Additional water 6.0 KG (Added after homogenization- part of aqueousphase) Resin/Water 20% 12.0 KG High amino 6.27 amine KG formaldhyderesin Water 5.73 KG

An emulsion mixture is prepared from premixtures as described aboveincluding: (1) an aqueous solution, (2) an internal phase mixture, and(3) an amine formaldehyde resin.

The aqueous solution was prepared by mixing 30 kg of a commerciallyavailable surfactant product including about 5% by weight ethylenemaleic anhydride in water. The resulting aqueous solution is maintainedat a temperature ranging from 60° C. to 90° C. and contained sufficientEMA to impart about 2.7% by weight EMA in the final emulsion slurry.

The internal phase mixture is a standard mixture for producing a greenthermochromic effect and suitably includes 50-80% by weight of analcohol/ester mixture as the carrier, 1% to 10% by weight of agreen-forming leuco dye, and 5% to 30% by weight of a phenolicdeveloper. The internal phase mixture weighs 18 kg, constituting 30% ofthe emulsion mixture by weight. The internal phase mixture is maintainedat a temperature ranging from 120° C. to 130° C.

The amine-formaldehyde resin solution is prepared by mixing 6.27 kg of acommercially available high amino anime formaldehyde resin with 5.73 kgof water. The amine-formaldehyde resin solution was maintained at atemperature ranging from 20° C. to 50° C. The amine formaldehydesolution weighs 12 kg, constituting 20% of the emulsion mixture.

The internal phase solution is poured into the aqueous solution underhigh shear conditions created by a homogenizer over 2-3 minutes. After asuitable emulsion develops, the amine-formaldehyde solution is pouredinto the emulsion over 1-2 minutes. At the end of the resin addition,the homogenizer is shut down and removed from the process. A largeimpeller type mixer is then engaged to keep the capsules suspended whilethe capsule walls form. This is done while maintaining a temperature offrom 80° C. to 90° C. An additional 6 kg of distilled water is added tothe slurry under mixing conditions to reduce high viscosity gelationwhich occurs after the polymer addition. At this point the emulsionmixture is complete.

A catalyst for polymerizing the resin is optionally next added. Thecatalyst may be a blocked amine p-toluene sulfonic acid. The catalyst isadded in an amount equal to 5% to 35% by weight of the amineformaldehyde resin. The pH of the resulting mixture was adjusted toabout 3.5 to 4 by addition of triethanolamine. Under the hightemperature and low pH, the amine formaldehyde resin polymerizes andaccumulates as the capsule wall around the internal phase. The resinwall crosslinks into a hardened shell over a period of 2-8 hours whilethe polymerization reaction occurred at a temperature from 80° C. to 90°C.

Working Example 2 Slurry Processing into a Microencapsulated Pigment forInk Manufacture

After polymerization, the slurry produced in the foregoing Example 1 hasa high kinematic viscosity ranging from 2000 to 4000 centipoise. Theslurry is approximately 40% by weight solids including capsules andother materials, together with approximately 60% water. In order toproduce a metal decoration ink, the bulk of the water needs to beremoved from the liquid slurry, thus reducing the amount of water from60% by weight percentage to a percentage of from 1% to 50% by weight.

Dewatering is to be accomplished by filtration, and may be assisted bychemical additives as are known to the art. Further dewatering may beaccomplished by introducing the filtered slurry into a jacketed vacuummixer, which is maintained at elevated temperature under high vacuumcondition. During the vacuum drying process the slurry is continuouslymixed to expose surface area to accelerate the drying process. Theslurry is, for example, dewatered to a concentration of 5% to 35%moisture. A final pigment is then suitable for processing into a metaldecorating ink capable of withstanding a high temperature oven curewithout extreme color loss. The ink also had improved transfer rheologywithout severe misting in high speed production lines.

Working Example 3 Various Coating Formulations

The following formulations use the presscake pigment from Example 1,which may be dispersed into the resin vehicle system using a 3-roll milland processed into a metal decoration ink. In one example of this, aroll milling process disperses the pigment into the ink vehicle forapplication as a metal decoration ink which is oven cured at atemperature of 200-230C for a time of 2-3 minutes.

Two Part Epoxy Coating

Part A (30% by weight of coating)

-   -   Thermochromic pigment (any color)*

Part B (70% by weight of coating)

-   -   Clear Coating (an epoxy coating available from Watson Standard        of Pittsburgh, Pa.)    -   * This material may be purchased on commercial order from        Chromatic Technologies, Inc. of Colorado Springs Colorado, and        may include for example S5BOXX3105W, a blue thermochromic slurry        that goes from a colored to colorless state when the temperature        exceeds 31° C.

Two Part Epoxy Coating

Part A (60% by weight of coating)

-   -   45% Thermochromic Pigment (any color)*    -   50% Epoxy resin (for example Epon 863 available from Lawter of        LaVergne, Tenn.)    -   3.3% Dispersing aid (for example Disperbyk 2025 available from        Byk of Wallingford, Conn.)    -   1.7% Curing agent (for example Ancamine 2458 available from Air        Products of Allentown, Pa.)

Part B (40% by weight of coating)

-   -   85% Clear Coating (an epoxy coating available from Watson        Standard of Pittsburgh, Pa.)    -   15% Solvent to reduce viscosity (for example, butyl carbitol        acetate, xylenes, or methyl isobutyl ketone)    -   * This material may be purchased on commercial order from        Chromatic Technologies, Inc. of Colorado Springs Colorado, and        may include for example S5BOXX3105W, a blue thermochromic slurry        that goes from a colored to colorless state when the temperature        exceeds 31° C.

One Part Polyester Coating

-   -   20% (w/w) Thermochromic Pigment (any color)*    -   13% Polyester resin (for example, Decotherm 290 available from        Lawter of LaVergne, Tenn.)    -   0.5% (w/w) Dispersing aid (for example, Byk 370 available from        Byk of Wallingford, Conn.)    -   7% (w/w) Curing agent 1 (for example, Cymel 328 available from        Cytec Industries of Woodland Park, N.J.)    -   1.5% (w/w) Curing agent 2 (for example, imidazole available from        Aldrich of St. Louis, Mo.)    -   2% (w/w) Wax (for example, Fluoron 735 available from Lawter of        LaVergne, Tenn.)    -   30% (w/w) Solvent (for example, ethyl-3-ethoxypropionate        available from Univar of Redmond, Wash.)    -   26% (w/w) Clear Coating (an epoxy coating available from Watson        Standard of Pittsburgh, Pa.)

One Part Epoxy Coating

-   -   15% (w/w) Thermochromic Pigment (any color)*    -   10% (w/w) Resin (for example, Epon 896 available from Lawter of        LaVergne, Tenn.)    -   1.5% (w/w) Dispersing aid (for example, Disperbyk 112 available        from Byk of Wallingford, Conn.)    -   0.5% (w/w) Curing agent 1 (for example, Nacure 2500 available        from King Industries of Norwalk, Conn.)    -   4% (w/w) Curing agent 2 (for example, Cymel 325 available from        Cytec Industries of Woodland Park, N.J.)    -   1.5% (w/w) Wax−0.5 wt % (for example, Ultrapoly 211A available        from Lawter of LaVergne, Tenn.)    -   5% (w/w) Solvent 1 (for example, Heloxy Modifier 62 available        from Lawter of LaVergne, Tenn.)    -   21.5% (w/w) solvent 2 (for example, ethyl-3-ethoxypropionate        available from Univar of Redmond, Wash.)    -   41% (w/w) Clear Coating (an epoxy coating available from Watson        Standard of Pittsburgh, Pa.)

Inkjet Ink

Ingredient Weight % Thermochromic Pigment Slurry 30%  (20% water)Glycerol 10%  1,2-hexanediol 2% 1,2-propanediol 0.4%  Tripropyleneglycol methyl ether 2% Trimethylol propane 5% Surfynol 104E 0.5% Deionized water balance 100.0%   

It will be appreciated also that the thermochromic pigments describedherein may be used in place of other pigments reported for use in inkjet printer inks, for example, as described in U.S. Pat. No. 6,132,501issued to Scaringe et al. and U.S. Pat. No. 7,354,962 issued to Akers etal.

Accordingly, it is to be understood that the embodiments of thedisclosure herein described are merely illustrative of the applicationof the principles of the disclosure. Reference herein to details of theillustrated embodiments is not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe disclosure.

1-6. (canceled)
 7. A dewatered slurry comprising: encapsulatedthermochromic systems comprising: an internal phase including a leucodye and a developer for said leuco dye; and a resin; wherein saidencapsulated thermochromic systems have a mean by volume particle sizediameter of less than 1 micron; an anionic surfactant in an amount whichconstitutes greater than 2% of said dewatered slurry by weight; and achemical additive in an amount effective to facilitate dewatering withsaid anionic surfactant in place to provide said dewatered slurrycomprising less than 60% water by weight.
 8. The dewatered slurry ofclaim 7, wherein said anionic surfactant is selected from the groupconsisting of: polystyrenesulfonate, styrene copolymers,polyvinylsulfonatester salts, polyvinylsulfonates, maleicanhydridestyrene copolymer, maleic anhydride-isobutylene copolymer,maleic anhydride-ethylene copolymer, maleic anhydride-methyl vinyl ethercopolymer, polyvinyl alcohol (saponified product),carboxymethyl-modified polyvinyl alcohol, gum arabic, polyacrylates,polyacrylate derivatives, acrylate copolymers, carboxymethyl cellulose,gelatin, pectin, pullulan, phtahalated gelatin, succinated gelatin,cellulose sulfate ester salt, and alginic acid.
 9. The dewatered slurryof claim 7, wherein said anionic surfactant comprises ethylene maleicanhydride.
 10. The dewatered slurry of claim 7, wherein said resincomprises amine formaldehyde resin.
 11. The dewatered slurry of claim 7,wherein said dewatered slurry comprises 20% to 40% water by weight. 12.The dewatered slurry of claim 7, wherein said dewatered slurry iscombined with an ink vehicle to generate an ink.
 13. The dewateredslurry of claim 7, wherein said dewatered slurry is combined with acoating vehicle to generate a coating.
 14. The dewatered slurry of claim13, wherein said coating comprises a metal decoration coating.
 15. Thedewatered slurry of claim 14, wherein said metal decoration coating isformulated for coating a beverage container.
 16. The dewatered slurry ofclaim 7, wherein said encapsulated thermochromic systems, uponactivation, achieve a color selected from the group consisting of: blue,green, yellow, and cyan.
 17. The dewatered slurry of claim 7, furthercomprising a photochromic dye.
 18. The dewatered slurry of claim 7,where said dewatered slurry is made from a slurry comprising: saidinternal phase including said leuco dye and said developer for saidleuco dye; said resin; and an aqueous phase including said anionicsurfactant in an amount which constitutes greater than 2% of said slurryby weight; wherein said amount of said anionic surfactant is effectiveto produce said encapsulated thermochromic systems which have said meanby volume particle size diameter of less than 1 micron.
 19. Thedewatered slurry of claim 18, wherein said effective amount of saidanionic surfactant is in a range of 1% to 10% of said aqueous phase byweight.
 20. The dewatered slurry of claim 18, wherein said aqueous phaseis in a range of 40% to 70% of said slurry by weight.
 21. The dewateredslurry of claim 18, wherein said internal phase is in a range of 23% to35% of said slurry by weight.
 22. The dewatered slurry of claim 18,wherein said leuco dye is in a range of 1% to 10% of said internal phaseby weight.
 23. The dewatered slurry of claim 18, wherein said resin is aresin solution in a range of 15% to 28% of said slurry by weight. 24.The dewatered slurry of claim 23, wherein said resin solution comprisesamine formaldehyde resin in a range of 40% to 60% of said resin solutionby weight.